Colorimetric test strips or reagent strips for water analysis are known. Areas of use include tap water quality testing, industrial and environmental testing, pool and spa testing, lake and stream testing, aquarium testing and other types of water testing. Simple, quick and accurate testing is advantageous, and a test strip must have the necessary detection capability.
For analysis of copper or iron cations, these test strips typically consist of a plastic support having affixed thereto a porous, absorbent carrier bearing an appropriate indicator. Illustrative is the copper (I)-detecting test stick of U.S. Pat. No. 3,748,096, in which the absorbent carrier is impregnated with an indicator composition that includes a reducing agent for converting copper (II) to copper (I). Also illustrative is an iron (II)-detecting test kit, which in addition to test strips includes a sample-measuring tube, a supply of a reducing agent for converting iron (III) to iron (II), and a measuring spoon for adding the appropriate quantity of reducing agent to the sample volume. "Total copper" by which is meant copper (II) and copper (I), or "total iron" by which is meant iron (III) and iron (II), are measured by these particular analyses.
An immersible reagent strip including an aperture, and a carrier having exposed opposite faces, is described in U.S. Pat. No. 5,491,094, which issued on Feb. 13, 1996 on application Ser. No. 08/253,959, filed on Jun. 3, 1994. An immersible test strip including a wick member enclosed in a fluid impervious sheath, and an aperture exposing a portion of the wick member, is illustrated by U.S. Pat. No. 4,092,115.
Also known as exemplified by U.S. Pat. No. 3,901,657, is an immersible test strip having a plurality of superposed carriers. Likewise known as illustrated by U.S. Pat. Nos. 3,006,735, 4,275,031, and 4,904,605, is a test strip having a plurality of spaced apart carriers affixed to or coated onto a support for multiple analyses upon immersion in a water sample.
There continues to be a need for an improved immersible colorimetric test strip, and in particular an improved immersible test strip for quantitative analysis of copper (I) or iron (II), and especially of total copper or total iron. Beneficially, there would be enhanced sensitivity and accuracy, yet simplicity of handling. It would be advantageous for the test strip to be economical to manufacture.